1. Field of the Invention
The invention relates generally to an adjustable axial piston machine with a bent axis design and more particularly to such a machine having a rotatable cylindrical drum with a plurality of cylindrical bores formed therein and a piston located in each bore. One end of the cylindrical drum is mounted on a shaft and the other end is supported on a swivel carriage. The swivel carriage has a pair of channels formed therein one of which is connected with a fluid supply channel and the other of which is connected with a fluid discharge channel. The swivel carriage is supported by at least one piston against a guide surface formed on the machine swivel carriage housing so that the cylindrical drum and the support piston or pistons carrying the swivel carriage are movable in the same direction. The cylindrical drum has openings in one end face connected with cylindrical boreholes formed in the swivel carriage and is rotatable relative to the swivel carriage. Servo pistons are provided for adjusting the angle between the axis of the cylindrical drum and the guide surface on the machine swivel carriage housing to change the length of the stroke of the pistons in the cylindrical bores in the cylindrical drum.
2. Description of the Prior Art
In known adjustable axial piston machines of this type, the swivel carriage is hydrostatically relieved with respect to the swivel carriage guide surface for easy adjustability. In order that the release does not increase with increased adjustment of the swivel carriage angle and thereby form a gap resulting in leakage losses the fluid feed and fluid discharge channels on the side of the swivel carriage facing the swivel carriage guide surface are formed to be increasingly more narrow. Due to the limited channel cross section a high flow rate of the fluid occurs with large adjustment angles resulting in the loss of hydraulic fluid.
Additionally, the adjustment of the angle between the cylindrical drum axis and the guide surface in the prior art machines, i.e., the adjustment of the piston stroke and thus the power, is by a servo-operated piston that is located in a control head on the outside of the swivel carriage guide housing since the servo piston is connected with the swivel carriage. When large adjustment angles are required, a long servo piston stroke is required and a large control head is necessary to house the servo piston which results in undesirable increased machine dimensions.